1. Field of the Invention
This invention relates to a sample analyzer for analyzing a sample by use of near field light emitted from a nano-aperture of a probe.
2. Description of the Related Art
There has been known a near field optical microscope such as a scanning photon type tunnel microscope as a system which can analyze the shape and/or structure of sample which is smaller than a wavelength of light. In the near field optical microscope, near field light (evanescent light) is projected onto the surface of a sample through a nano-aperture of a probe and the intensity of scattered light generated by interaction between the surface of the sample and the near field light, that is, disturbance of the near field (evanescent field) by the surface of the sample is detected, and information on the shape and/or structure of the surface of the sample is obtained by causing the probe to scan the surface of the sample and taking a scattered light intensity detecting signal in time series as a function of the position of the probe.
The probe with a nano-aperture is generally prepared by sharpening an end of an optical fiber by etching, depositing metal film on the sharpened end and removing a part of the metal film.
Even with the near field optical microscope, information on more detail of the sample such as orientation of molecules at each part of the surface of the sample cannot be obtained.
Further in the probe with a nano-aperture, propagation loss of light varies according to the shape of the nano-aperture, and the intensity distribution pattern of the near field light, which is an evanescent wave, varies according to the shape of the nano-aperture, which affects the result of the analysis. Accordingly, the shape of the nano-aperture of the probe must be evaluated in order to check the performance of the probe.
This check has been conventionally carried out by observation through an electron microscope. However this method is a destructive inspection and cannot be used for checking a probe to be actually used.
Further since the intensity distribution pattern of the evanescent light is also related to the state of polarization of the light which enters the probe, it is required when a probe is used to determine in advance the correlation between the intensity distribution pattern of the evanescent light and the state of polarization of the light which enters the probe and to select an optimal state of polarization. For this purpose, the intensity distribution pattern of the near field light must be actually detected and conventionally the intensity distribution pattern of the near field light through a probe to be checked is detected by scanning of another probe.
However this method is disadvantageous in that it requires skill, takes a long time and is low in yield. Further since the probe for measurement affects the intensity distribution pattern of the near field light emanating from the probe to be checked, reliability of evaluation is low.
In various instruments using the near field light other than the near field optical microscope, devices with a nano-aperture are employed and evaluation of the nano-aperture is required.